1. Field of the Invention
The invention relates generally to filtering devices for filtering suspended solids from a liquid stream and, more particularly, to a filtering device and method using ozone to disinfect both the liquid stream and the filtering media.
2. Description of the Prior Art
In order to conserve water, many industrial facilities recycle and reuse waste water or turbid water streams. However, before such water can be reused, debris in the stream must be removed so that it does not damage equipment. Various filtration devices are known for removing debris from a waste water stream or turbid water stream to clarify the water prior to its use in, for example, manufacturing and industrial facilities, such as power plants, as well as municipal facilities, such as conventional potable water systems. These known filtration devices include conventional "deep bed sand filters". One such deep bed sand filter is disclosed in U.S. Pat. No. 5,277,829 to Ward. In conventional deep bed sand filters such as described in the Ward patent, a downwardly flowing filter media, for instance sand, is placed in counterflow to the upwardly flowing waste water stream. Debris is removed from the waste stream by being trapped in the downwardly flowing sand. Although such deep bed sand filters generally do a good job of removing relatively large debris material from the waste stream, there are problems associated with these known deep bed sand filters.
For example, while the filter media, usually a sand bed, removes relatively large particulate debris from the waste stream, the filter media has little or no effect upon biological contaminants, such as bacteria, or upon small organic material. Therefore, the effluent from these conventional deep bed sand filters must be further purified downstream of the sand filter to try to remove the biological and organic contaminants. The need for such downstream purification systems increases the costs of manufacturing and maintaining the filtration system as well as the time required to complete the treatment of the waste stream. Due to the presence of bacteria and organic matter in the waste stream, these conventional deep bed sand filters rapidly become bacteria and organic growth havens, leading to a foul odor which is unpleasant to work around. Also, organic growth in the filter media contaminates the filter media and hinders the filtering ability of the filter media. Therefore, the sand bed in these conventional deep bed sand filters must be frequently replaced. This frequent removal and replacement of the sand bed is time consuming and increases the operational costs of the filtering device. Additionally, the size of the particulate matter in the waste stream which can be removed by conventional deep bed sand filters is dependent upon the type of filtering media used. With conventional deep bed sand filters, very small debris, such as small organic material, may escape being trapped in the sand bed altogether.
Therefore, it is an object of the invention to provide a device for filtering particulate material from a fluid stream, such as waste water, which also disinfects the filter media and the fluid being treated to help prevent bacterial and organic growth in the device and the foul odors and decreased filtering capacity associated therewith. It is additionally an object of the invention to provide a filtering device in which relatively small organic debris may be oxidized to help remove such small organic debris from the waste stream. It is also an object of the invention to provide a filtering device in which additional bacterial purification is not needed downstream of the filtering device. It is further an object of the invention to provide a filtering device which cleans and disinfects a fluid stream at decreased media and maintenance costs.